The first loco bought with the intention of an eventual South Wales-themed layout in N was the then-new Dapol 57XX pannier. At the time I could only test it easily under DCC, so I put in a small decoder and tried it on the American layout. It was rubbish. but I (naively) assumed it would  improve with some running-in and so on. Not a chance! After I got it out of its box again for Paynestown, I was reminded how hopeless it had been to begin with. It would only do very jerky starts, couldn't run at slow speed, and was prone to stalling at any excuse, seemingly often at random on otherwise plain ttrack. Absolutely no good at all for the kind of work required on a BLT although it might just have been acceptable on a roundy-roundy.

No amount of tweaking or running-in made much diference, so I investigated further by dismantling the thing. I found that the root of the problem was with the motor itself, which needed quite a large kick voltage to start turning, even when not under any load. You could hear it humming as it tried to move. I don't know if this was just a bad motor, or whether Dapol skimped on the motors generally, but it's not a characteristic I've run into with any of the small can motors I've encountered, all of which which start turning silently almost as soon as voltage is applied.

Seeking a solution, I found that Tramfabriek do a range of drop-in coreless motors for Dapol engines. While the 57XX wasn't one of them, I took a punt that the one for the Terrier might work in a pinch. It wasn't too expensive, and I reasoned that if it couldn't be made to work at all, I'd still have a nice motor to put in a Terrier! The main issue was going to be the compatibility of the shaft diameters, and whether the Tramfabriek worm gear would play nicely with the existing gears, or would need swapping for the original one.

With the body off, I fashioned a motor-mount from a  piece of Evergreen I-section plastic and tacked it and the motor in place with dabs of cyano, just as an first go. It seemed to work quite nicely - certainly a vast improvement on what had been there before. I can't vouch for it being mechanically "correct" but as a bodge, it works for me - although I'll stress that the kit is not meant for the Pannier.

With the original mechanism, the motor is lodged up in the pannier body. Removing it frees up a lot of space which can now be profitably filled with lead, adding to the all-up weight of the loco.

I still wasn't 100% happy, so I took a leaf from a thread I found on Rmweb about improving a 2mm conversion of the pannier, by adding wiper pickups. I made mine from the thinnest brass I had, then added blobs of solder to make the contact point. They then need careful adjustment to make sure they're scraping the rails, but at the same time not lifting the loco.

https://www.rmweb.co.uk/topic/64660-Dapol-pannier-a-haynes-manual/

Mine aren't very neat (a first go) but it's surprising how well they're hidden once the loco is reassembled:

They just tuck in between the wheels and behind the brake rods, and they're not even painted yet. If I can source some thinner brass, I'll make a second attempt but they work for now.

Here's a short clip showing the loco in action:

It still needs to be "driven" but previously it couldn't complete any sort of manoevre without at least a stall, so this is a great step in the right direction.

Incidentally, aside from the motor issues, I think the other possible flaw is that the chassis is too rigid. The Bachmann and Sonic locos all have a tiny amount of play in the axles, equating to a crude kind of compensation. With the Dapol one, it's so rigid that there's often going to be just one wheel in contact with the rails on one side, which then only needs to hit a tiny bit of dirt to stall.

Dapol seem to be revisiting their earlier N locos so perhaps the 57XX will get a better mechanism in due course. The body is exquisite, so it's certainly one well worth upgrading.